1. Field of the Invention
The present invention relates to a governor device for controlling the speed of an engine in response to the change in revolution of said engine.
2. Description of the Prior Art
A conventional governor device of centrifugal weight type has long been widely used which is arranged to effect the control of the engine speed by a displacement of a governor weight caused when the weight is subjected to a centrifugal force based upon the engine revolution.
Such conventional governor device, however, has a number of disadvantages to be solved. For example, lubrication must be performed in order to prevent a slide portion between a rotating and a non-rotating members from wearing. In addition, highly precise components and reliability of assembly are also required to achieve the stable control of the engine speed. Further, there is a limitation in amount and displacement of the governor weight, which leads to narrower range of control stroke and reduced ability of setting for driving force transmitted. Furthermore, the specific gravity of the governor weight will vary depending upon the displaced position of the governor weight due to the centrifugal force. Therefore the control characteristic of the governor device becomes significantly non-linear.
Another type of the governor arrangement is also proposed in which a torque generator to be driven by the engine is used instead of the centrifugal weight type governor. The torque generator produces a rotational torque on its stator without contacting the rotating part of the engine and the rotational torque produced is transmitted to the engine throttle valve to adjust the degree of opening thereof (Refer to Japanese Patent Publication Nos. 22617-1980 and 22618-1980).
This prior art governor arrangement, however, does not rapidly operate in response to the change in engine revolution due to its conversion scheme wherein the dynamic change in engine revolution is converted into a static change while controlling the output of said torque generator. In addition, installing of such torque generator within the engine presents certain problems such as the complication in construction and the increase in bulk.
Further the other type of the governor arrangement is developed in which in order to improve the easiness in installing the governor device in the engine, especially the overhead cam shaft type engine, the governor device of the centrifugal weight type as stated above is incorporated into the camshaft and is operated in response to the rotation thereof (Refer to Japanese Patent Laid Open No. 207836-1986).
This governor arrangement also has the disadvantages due to the centrifugal weight type governor as stated above.
More particularly, in the arrangement of the prior art governor device, because of the cooperation of the device with the rotational axis of the engine, it is installed in the body of engine itself. Referring now to FIG. 21, the degree of opening of the throttle valve 57 is adjusted by moving a link 59 mounted on the throttle axis 58 of the carburetor throttle valve 57 by a control cable 56 extending from the governor device and coupled to said link 59.
Such drive means for driving the throttle axis 58 by the link 59, however, produces a change in torque for rotating the throttle axis 58, depending upon the degree of opening of the throttle valve 57. In this regard, greater the degree of opening of the throttle valve 58, smaller the torque produced, thereby it may be insufficient to drive the throttle valve 57.